The Geass of Fear:
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Requires eye contact and can only be used on elder people. (<20 years)
The victim would feel an irrational fear and will be unable to move. Prolonged use can lead to severe trauma.
After the use the victim will try to avoid the "caster" and if it is impossible to flee he will do anything the "caster" asks him to do. It can be used best for interrogation purposes.
The Geass of Sleep:
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People in a 50 meter area are affected (they fall asleep for 5 hours)
Does not require eye-contact, but can only be used once a day. If it is used twice a day it does not work properly and the people will only feel tired. With time, the geass becomes more powerful and an eventual second use will have stronger effects.
Excessive use can active it permanently and the geass will be used immediately after the "caster" wakes up. Of course it has the drawback that people will feel sleepy wherever he goes.
The geass of truth:
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It is impossible to lie to the "caster" when used.
Requires eye-contact.
Ideal for interrogations.
The geass of lie:
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The victim believes everything the caster says. (If the caster says that ink tastes good and is good for his health, the victim would start drinking ink.)
Requires direct eye contact and it cannot be used during full moon. Also the effect lasts only until the next full moon.
Ideal for political carrier.
The geass of awesomeness:
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Everyone thinks the user is awesome. (If the user starts selling papers with his name written on it, everyone the geass is used on, will buy it and cherish the piece of paper for the rest of their life.)
The victim has to look in the eyes of the "caster" for 5 minutes.
The geass of silence:
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The caster can forbid the victim to say something. Every time the victim tries to speak or write about the incident he will be unable to.
Requires eye contact and can only be used once on a person.
Ideal to keep secrets.